1. Field of the Invention
The present invention relates to a memory system and a host device, and is applied to, for example, a memory card formatted into an additional write file system such as the UDF file system, and a host device and the like corresponding thereto.
2. Description of the Related Art
As means for efficiently writing data onto a memory system (for example, an SD card (registered trade name), and the like) into which a nonvolatile storage device such as a NAND flash memory or the like is incorporated, means to which an additional write file system such as the UDF-VAT system from the host device is applied is proposed (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2006-40264).
Here, in an overwrite type file system such as the FAT file system, when an unnecessary file is deleted, the free space of the storage area is increased correspondingly.
However, in the additional write file system such as the UDF-VAT system, even when a file is deleted, information indicating “the file has been deleted” is additionally written onto the nonvolatile memory. For this reason, the free space of the storage area cannot be increased by only deleting the file.
Further, in the additional write file system, in order to increase the free space of the storage area by deleting a file, it is necessary to, after deleting the file, rewrite data of addresses after the area in which the data of deleted file has been stored in sequence to tighten the area so that no unnecessary area is present in the addresses of the deleted area, and rewrite the pointer of the file information (so-called garbage collection). As a result of this, there is a tendency in the system to take much time in processing, and worsen the usability. Further, there has been a drawback in the system that the number of times of write to the NAND flash memory becomes large.